US Federal Rules API: CFR text as of a date + Federal Register

One call answers "what does 21 CFR 101.9 say today, when did it last change, and which Federal Register rule changed it?": the section as plain text from the eCFR (as in force today or on any date since 2017), its amendment history, and the final rules behind each change. It also lists what changed in a CFR part since a date ("15 CFR 744 this week") and returns Federal Register documents by number or search. Built for AI agents doing regulatory, compliance and export-control work, and for people who want a sourced answer without learning two APIs.

Pricing (pay per event): $0.005 per CFR section returned (section), $0.002 per Federal Register document returned (document). A citation that can't be read, a section that doesn't exist or an empty result fails or ends in seconds and costs nothing.

What you get

Real output for {"citation": "21 CFR 101.9"}, run on 2026-11-06 (text and amendment list shortened here; the full row is 22 KB):

{
  "schema_version": "1",
  "record_type": "cfr_section",
  "query": "21 CFR 101.9",
  "citation": "21 CFR 101.9",
  "cfr_title": 21,
  "cfr_title_name": "Food and Drugs",
  "part": "101",
  "subpart": "A",
  "section": "101.9",
  "unit_type": "section",
  "heading": "§ 101.9 Nutrition labeling of food.",
  "as_of": "2026-11-04",
  "text": "(a) Nutrition information relating to food shall be provided for all products intended for human consumption and offered for sale unless an exemption is provided for the product in paragraph (j) of this section.\n(1) When food is in package form, the required nutrition labeling information shall appear on the label in the format specified in this section.\n(2) When food is not in package form, the required nutrition la ...",
  "text_chars": 19521,
  "text_truncated": true,
  "source_note": "[58 FR 2175, Jan. 6, 1993]",
  "removed": false,
  "latest_change_date": "2023-05-24",
  "changed_since": null,
  "amendments": [
    {
      "date": "2023-05-24",
      "substantive": true,
      "removed": false,
      "fr_documents": [
        {
          "document_number": "2023-10602",
          "citation": "88 FR 33550",
          "title": "Food Labeling, Infant Formula Requirements, Food Additives and Generally Recognized as Safe Substances, New Dietary Ingredient Notification; Technical Amendments; Correction",
          "type": "Rule",
          "publication_date": "2023-05-24",
          "effective_on": "2023-05-24",
          "url": "https://www.federalregister.gov/documents/2023/05/24/2023-10602/food-labeling-infant-formula-requirements-food-additives-and-generally-recognized-as-safe-substances"
        }
      ]
    },
    {
      "date": "2023-03-24",
      "substantive": true,
      "removed": false,
      "fr_documents": [
        {
          "document_number": "2023-05418",
          "citation": "88 FR 17710",
          "title": "Food Labeling, Infant Formula Requirements, Food Additives and Generally Recognized as Safe Substances, New Dietary Ingredient Notification; Technical Amendments",
          "type": "Rule",
          "publication_date": "2023-03-24",
          "effective_on": "2023-03-24",
          "url": "https://www.federalregister.gov/documents/2023/03/24/2023-05418/food-labeling-infant-formula-requirements-food-additives-and-generally-recognized-as-safe-substances"
        }
      ]
    },
    { "date": "2016-12-19", "substantive": true, "removed": false, "fr_documents": null }
  ],
  "ecfr_up_to_date_as_of": "2026-11-04",
  "source_url": "https://www.ecfr.gov/on/2026-11-04/title-21/section-101.9",
  "provided_by": "Bosco Labs (boscolabs.dev)",
  "api_url": "https://www.ecfr.gov/api/versioner/v1/full/2026-11-04/title-21.xml?section=101.9",
  "warnings": ["text cut at 20000 characters (of 121140); raise maxTextChars or read source_url."],
  "retrieved_at": "2026-11-06T08:37:27+00:00",
  "duration_seconds": 1.62
}

• text: plain text as in force on as_of, one line per paragraph ((a), (1), (i)), tables as cell | cell rows. Long sections are cut at maxTextChars (default 20,000) and flagged.
• amendments: every amendment date in the eCFR's history (newest first), with fr_documents: the final rules affecting that CFR part that took effect (or were published) on that date. null means not looked up (only the 5 newest dates are), [] means none found.
• source_note: the CFR source note with the Federal Register citation that created the section.
• source_url is the eCFR page for people (cite it). Programs should fetch api_url: ecfr.gov web pages send automated clients to a CAPTCHA, the API does not.

A Federal Register document row ({"documentNumber": "2026-17231"}) has citation (91 FR 54658), title, type, action, abstract, dates, agencies, publication_date, effective_on, comments_close_on, cfr_references (["15 CFR 744"]), docket_ids, regulation_id_numbers, the FederalRegister.gov page as source_url and the official govinfo.gov pdf_url.

Input

{ "citation": "21 CFR 101.9", "asOf": "2024-01-01" }

What changed in a part: {"citation": "15 CFR 744", "since": "2026-08-01"} returns one row per section or appendix of the part changed since that date (most recent first, up to 25), each with its current text and the rules behind its newest change (the 5 newest change dates per run are looked up). On 2026-11-06 that was Supplement No. 4 (the Entity List, changed 2026-08-24 by documents 2026-17231 and 2026-17230) and Supplement No. 2 (2026-08-14, "Streamlining Export Controls for Drone Exports"). If nothing changed, the run says so and when the part last changed.

Federal Register search: {"search": "entity list", "agency": "BIS", "since": "2026-06-01"} returns matching documents, newest first. Add citation to keep only documents affecting that CFR part.

Use from an AI agent (MCP)

Agents can call this Actor as a tool through the Apify MCP server. Add this server URL to your MCP client (Claude, Cursor, VS Code, ...):

https://mcp.apify.com?tools=bosco_labs/us-federal-rules

It loads this Actor as a tool, plus the tools that read its results (get-actor-run, get-dataset-items). The hosted server signs you in with OAuth, or accepts your Apify token as Authorization: Bearer <APIFY_TOKEN>.

Example prompt: "What changed in the Export Administration Regulations part 744 since August, and which Federal Register notices did it? Link the sources." The agent passes:

{ "citation": "15 CFR 744", "since": "2026-08-01" }

Output for agents: small JSON rows (a section is typically 5-25 KB with the default text cap), stable snake_case fields, ISO dates, null for unknown, a source link per row and per linked rule. A unit whose text eCFR fails to send in a part listing comes back with text: null, a warning and no charge. warnings says in plain words when text was cut, a date was capped at the eCFR's latest data, or more results matched than were returned. A section lookup takes 1-2 seconds after start-up (measured 1.6 s for 21 CFR 101.9); a part with changes 2-7 seconds for a few units (the Entity List alone is 1.4 million characters of XML), up to about a minute for 25 units, which are downloaded two at a time to stay within eCFR's limits.

Cost: $0.005 per section, $0.002 per document, billed to the Apify account the MCP server is signed in with. Nothing is charged for a failed or empty lookup, or for a section row without text.

FAQ

Where does the data come from? Only from the two official APIs of the Office of the Federal Register (National Archives) and the Government Publishing Office: the eCFR versioner API (point-in-time CFR text and version history) and the FederalRegister.gov API (documents since 1994). Both are keyless. The text is converted from XML to plain text and nothing else is changed.

May you resell this? Yes. FederalRegister.gov and eCFR.gov state: "Any person may reproduce or republish any material appearing in any regular or special edition of the Federal Register (1 CFR 2.6). There are no restrictions regarding what is reproduced, who can reproduce it, or where it can be reproduced." Works of the US Government have no copyright (17 U.S.C. 105), and GPO's e-CFR guide says "there are no restrictions on re-use of information in the e-CFR documents". We don't use NARA or OFR seals or CFR logos and don't claim to be an official edition. Sources: About this site, govinfo policies, e-CFR XML guide.

Is the eCFR text the law? It is, in the OFR's words, "authoritative but unofficial". The official CFR is the annual print edition on govinfo.gov, kept current by the daily Federal Register. For legal research, verify against the official editions; each document row links the official govinfo PDF (pdf_url). This is not legal advice.

How exact is the link between a change and a Federal Register rule? The Federal Register indexes documents by CFR part, not section. For each amendment date we list the final rules that affect the same part and took effect (or were published) that day: in practice that is the rule that made the change, but on a busy day it can include a rule that changed a neighbouring section. Each comes with its title and link so an agent can check. Only the 5 newest amendment dates per run are looked up (older ones show fr_documents: null); in a part listing that is each unit's newest change, for the 5 most recent dates. If the Federal Register lookup fails, the row is kept with fr_documents: null and a warning.

How current is it? Live. The eCFR is updated daily and is usually 1-2 days behind the Federal Register (ecfr_up_to_date_as_of); an asOf later than that returns the latest text with a warning. The point-in-time history starts around January 2017; earlier dates fail with the first available date.

Can it diff two versions or return one paragraph? Not yet. A section is returned whole (a citation like 21 CFR 101.9(c)(8) returns all of 101.9 with a warning), and "what changed" is answered by dates and the rules that made the change, not a text diff. Huge appendices such as the Entity List are cut at maxTextChars (raise it up to 500,000).

Which CFR units work? All 50 titles: sections, and appendices or supplements (

15 CFR 744 Supplement No. 4

Personal data? None is requested. Federal Register documents and CFR appendices can name people or companies (e.g. the Entity List); they are returned only as published.

Content: Office of the Federal Register (National Archives) and US Government Publishing Office, via ecfr.gov and federalregister.gov. Not an official legal edition.